根系损伤强度对不同大小毛白杨生长及光合特性的影响

[Objective]To investigate the effects of different morphological sizes and root-breaking transplanting intensities on the growth,biomass allocation and photosynthetic characteristics of poplar,and to provide theoretical basis and guidance for the response of morphologically different poplars to root damage and countermeasures.[Methods]A two-factor experimental design was adopted,and two types of seedlings(height 317.44cm,diameter at breast height 14.3mm,diameter at ground leve l29.95mm)and small seedlings(height 154.18cm,diameter at breast height 4.43mm,diameter at ground level 12.44mm)were screened at the end of the season in the 20-gallon buckets of the one-year old"beilin Xiongzhu No.1"Populus tremula.))2 forms of seedlings,in early March of the following year with low intensity damage(T1-10 times the diameter of the ground),high intensity damage(T2-4 times the diameter of the ground),to simulate the different intensity of root-breaking starting seedlings,while setting up no damage control group(CK)to simulate the unbroken root seedlings.Plant morphology,biomass dynamics and photosynthetic characteristics were measured to analyze the response of seedling morphology and size to root damage intensity.[Results]The intensity of root injury and different morphological sizes of Populus tremula significantly affected biomass allocation and photosynthesis.Root damage significantly inhibited the growth of tree height and diameter at breast height of Populus tremula,and the response of large trees to damage was greater,with high intensity damage reducing tree height by 39.36%and diameter at breast height by 23.68%,while the effect of small trees was even smaller,with the same proportion of damage reducing tree height by 11.4%and diameter at breast height by 19.6%,and the effect of even lower damage intensity on the high growth of small trees was almost non-existent(P＞0.05),and the effect of the difference in diameter at breast height was significant,and tree height growth dynamics showed a significant difference.The growth dynamics of tree height showed significant differences,the small trees after damage still became an approximate"s"shaped growth curve,while the larger trees almost did not show growth peaks;the biomass of the various forms of aspen was significantly reduced after damage,the large trees in the high-intensity damage reduced the biomass by 59.62%,and the small tree damage seedlings reduced by 42.65%.The root dry weight and root to stem ratio were significantly smaller than those of the control group;the photosynthetic indexes of the trees in June,July and August after root damage were significantly lower than those of the uninjured treatment,and the gap between the photosynthetic indexes of the relatively small trees in August and those of the uninjured trees was significantly reduced,but there was still a significant difference.[Conclusion]Tree root damage responded similarly to plants of different sizes,with larger seedlings responding more clearly in the early stage of damage and requiring a longer recovery period,and smaller seedlings differing less from the uninjured treatment.Selecting smaller seedlings for transplanting within the range of seedling starting criteria is conducive to slowing down the adverse effects of seedling retardation,restoring growth faster,and improving silvicultural effect.Therefore,the superposition effect of seedling size and seedling starting intensity should be fully considered,which is of great significance for revealing the mechanism of seedling retardation in poplar afforestation in the same year.